1. Field of the Invention
The present invention relates to a controller driver, a mobile terminal using the same, and a display panel driving method.
2. Description of the Related Art
In general, a display panel such as a liquid crystal display (LCD) panel is driven by a controller driver. The controller driver is sometimes provided separately from the display panel, and the controller driver is sometimes provided with the display panel by using the COG (chip on glass) technique. The controller driver receives display data to be displayed, and stores the received display data in a display memory. Based on the display data stored in the display memory, the controller driver drives data lines of the display panel to display an image.
The image displayed on the display panel is often generated by synthesizing a plurality of images. The synthesis of the images is exemplified by an OSD (on-screen display) process in which a character image is superimposed on a background image, and a α blending process in which colors of pixels are blended between a plurality of images. By synthesizing the plurality of images, a variety of the images can be displayed on the display panel.
Japanese Laid Open Patent Application (JP-P2000-530898A) discloses a projection type display apparatus, in which a decoration effect image and an original image are synthesized. The conventional projection type display apparatus includes a frame memory for storing bit map data of the original image, a decoration effect bit map memory for storing bit map data of the decoration effect image, a decoration effect superimposing circuit, a liquid crystal display drive circuit and a liquid crystal panel. The decoration effect superimposing circuit generates a superimposed image data, in which the original image and the decoration effect image are superimposed, and supplies it to the liquid crystal display drive circuit (the controller driver). The liquid crystal display drive circuit drives the liquid crystal panel based on the superimposed image data.
In a display apparatus installed in a mobile terminal, a necessary space for the display apparatus must be reduced. Therefore, it is preferable to provide the function of synthesizing a plurality of images to the control driver of the mobile terminal, from the viewpoints of distribution of calculation processes and easy installation of the controller driver in the mobile terminal, unlike the above-mentioned projection type display device.
It is necessary to provide a memory with a capacity enough for storing each image for the controller driver, in order to give the controller driver the function of synthesizing the plurality of images. However, it is undesirable to install a large capacity of memory in the controller driver since this increases a cost. Especially, in the controller drivers in the mobile terminal such as a cellular phone and PDA (personal digital assistant), it is undesirable since the installation of a large capacity of memory results in the increase in power consumption and the spatial data size.
In this way, it is demanded to provide the controller driver having the function of calculating a plurality of images with smaller capacity of memory.